Gas metal arc welding (GMAW) is one of the most widely used processes in automated welding technologies. Its efficiency relies on the travel speed and wire melting rate. Increasing the welding current is the most effective way to improve them. However, the welding quality will decrease because of the unstable metal rotating spray transfer in the high-current GMAW which will aggravate the welding spatters and instability. To study the high-current metal transfer mechanism and then propose schemes of improvements and controls, a three-dimensional numerical model based on the volume-of-fluid (VOF) method is typically preferred. Unfortunately, the rotating spray transfer is extremely complicated, therefore the research community has focused on simplified models without considering the energy conservation to make analysis manageable for the unstable metal transfer process. Using our created model, the metal transfer of high-current GMAW with shielding gas of different conductivities has been studied by analyzing acting forces and fluid flows in the metal liquid column, especially for the contributions of the self-induced electromagnetic force, equivalent volume force of the capillary pressure of the surface tension (Named surface tension force in this work), static arc pressure. It is found that the unbalanced electromagnetic force greatly promotes the metal rotating motion in 500A MIG with pure argon shielding gas and it pushes the metal liquid column to rotate. Considering the arc constricting effect in active shielding gas by simply changing the arc conductivity, it is found that the metal liquid column no longer rotates, it turns to swing since the unbalanced electromagnetic force is large enough to break the rotating motion. The calculated results of the metal liquid column deflected angle and rotating/swing frequency agree well with the experiment of high-speed camera observations.